Originally Posted by ktappe
I understand what you are saying, but what I don't get is WHY it ever comes into play. If I am connected to a tower with a strong signal, no guessing should ever be needed--I should stay with that tower until my signal gets weak. When/if it does, only then should another tower (if there is one) with a stronger signal from my phone, take a "hand off" from the original tower. "Guessing" should not enter into it.
iPhone 2.0.2 user who again got several dropped calls last night while NOT MOVING with 5 bars of signal
It's important to remember that you are never "staying" with a tower. Even if we assume there is only one tower (ie, no 'hand-offs', which is its own fun little math game), the tower is only in contact with your phone once per cycle. So let's assume that AT&T's network has 60 cycles per minute (good for math, bad if they really only cycled once per second) and that you are in a completely flat surface with Line of Sight to the tower and "full bars": in second #1 you are at point x. The tower knows this and you have a connection. Where will you be in second #2? That depends:
- Are you standing still?
- Are you walking?
- Are you in a car moving 55mph?
- Are you in a rocket ship or airplane?
- Are you moving at warp 9.6?
The tower is dumb. It doesn't know if you are moving, what direction you are moving, or how fast you are moving. All it can ever know is position, and ID. So, now, draw a circle around your position in second #1 - everything in the circle represents everywhere in the universe you *could* be at second/cycle #2. The tower will send the info for *your* phonecall/whatever to every spot in that circle. The size of the circle needs to be as small as possible to minimize energy usage (think of the EMFs, think of your cellphone's battery...), but large enough that it doesn't "drop" you (if you are outside of the circle). This is optimization.
That's problem #1. Problem #2 is what happens if, at any cycle x, the tower can't find you? Let's say you momentarily pass through a lead box, blocking line of sight.... do you get clipped conversation ("can you hear me now?") or do you lose the call, altogether? This is AT&T's biggest weakness with their network: basically, their system craps the bed (for lack of a better term) if it can't find you in any given cycle (whether by bad estimation on its part or movement behind obstruction on your part). More towers or more power (think of the EMFs!) could ... help... but wouldn't solve this problem.
That's basically it. Verizon's cdma network is considered technologically older, but Verizon's proprietary tracking software does a much better job [imo, from anecdotal usage-experience] at keeping a connection - if it misses you at one cycle it just tries again at the next cycle and if you're still in the circle you're ok. AT&T's signal does this... poorly.
...oh, also - I had dropped-call problems with AT&T's GSM network a couple years back - I switched to verizon. It's not 3G, or GSM - it's the underlying tracking software. Blaming 3G is like blaming the mailman for bringing you bills.